MHC-Based Mating Preferences in Mus Operate through Both Settlement Patterns and Female Controlled Extra-Territorial Matings

Abstract

We have recently demonstrated strong MHC-based mating preferences in semi-natural populations of Mus (Potts et al., 1991). These preferences are primarily responsible for a 27% deficiency of homozygotes (relative to random mating expectations) observed in nine independent experimental populations. The strength of these preferences is sufficient to explain the majority of MHC genetic diversity found in natural populations of Mus. Here we expand our analysis of the nature of these mating preferences. Although the majority of the MHC-related non-random mating appears to be controlled by females traveling to nearby territories to mate with the resident male, a significant proportion (approximately one quarter) is explained by settlement patterns. MHC-related non-random settlement patterns were primarily due to an excess of settlement pairs that share no MHC haplotypes. Because males may exercise control over which females settle on their territories, this component of MHC non-random mating provides an explanation for the presence of male controlled MHC-based mating preferences found in laboratory studies (Yamazaki et al. 1976; Yamazaki et al. 1978; Yamazaki et al. 1988). The prevalence of studies showing male MHC mating preferences (Beauchamp et al. 1988) has been theoretically troubling due to the expectation that females should be the choosier sex (Partridge, 1988; Nei and Hughes, 1991). A companion paper in this volume (Manning et al.) provides the theory and empirical support for why female MHC mate choice may be diminished or lost during inbreeding.